Polynucleotides encoding useful polypeptides in Corynebacterium glutamicum ssp. lactofermentum

ABSTRACT

The present invention provides novel polypeptides and polynucleotides useful as biotechnological tools, specifically identified in a coryneform bacterium  Corynebacterium glutamicum  ssp.  lactofermentum  and methods of producing substances in organisms having enhanced or attenuated expression of these polypeptides and/or polynucleotides.

This application claims priority under 35 U.S.C. §120 to U.S.application Ser. No. 10/439,247, the entirety of which is incorporatedby reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to novel polynucleotides encoding proteinsuseful as biotechnological tools and for production of substances,specifically identified in a coryneform bacterium Corynebacteriumglutamicum ssp. lactofermentum and fragments thereof, polypeptidesencoded by the polynucleotides and fragments thereof, polynucleotidearrays comprising the polynucleotides and fragments thereof.

2. Brief Description of the Related Art

In the field of biotechnology, there needs many tools, for example, DNAligase, DNA polymerase, RNA polymerase, modification and restrictionenzymes, and so on. In this field, variation of genes or enzymes isimportant for extension of applicable objects. Furthermore, modificationand improvement of organisms are important for industrial production ofuseful substances, such as amino acids, nucleic acids, organic acids,sugars, and enzymes, (Faurie, R. and Thommel, J., Microbial Productionof L-Amino Acids, Springer Verlag, 2002; Harris, T. J. R., ProteinProduction by Biotechnology (Elsevier Applied Biotechnology Series),Aspen Publishers, 1990). For the aforementioned purpose, geneticengineering is one of the useful methods and many genes have been knownto be effective. Modification and restriction endonucleases, chaperoneproteins, enzymes that caytalyze important reactions, and transportersof important substances are useful for improving production ofsubstances in organisms.

For example, amino acids such as L-lysine, L-glutamic acid, L-threonine,L-leucine, L-isoleucine, L-valine, and L-phenylalanine are industriallyproduced by fermentation by using microorganisms that belong to thegenus Corynebacterium, Brevibacterium, Bacillus, Escherichia,Streptomyces, Pseudomonas, Arthrobacter, Serratia, Penicillium, Candida,or the like. In order to improve the productivity of amino acids,strains of the aforementioned microorganisms that have been isolatedfrom nature or artificial mutants thereof have been used. Variousexamples of modification of genes, such as amplification, deletion, andpoint mutation by using recombinant DNA techniques to increase theL-amino acid-producing ability have been disclosed (Faurie, R. andThommel, J., Microbial Production of L-Amino Acids, Springer Verlag,2002).

SUMMARY OF THE INVENTION

An object of the present invention is to provide novel tools or measuresin the biotechnology field. In addition to usage of genes itself,modification of genes, such as amplification, deletion, and pointmutation by using recombinant DNA techniques provides an efficientmethod to improve the process of substance production.

Such a process includes orgamisms or cells, which express a proteincomprising an amino acid sequence selected from the group consisting ofSEQ ID NO:2, SEQ ID NO:4, SEQ ID NO:6, SEQ ID NO:8, SEQ ID NO:10, SEQ IDNO:12, SEQ ID NO:14, SEQ ID NO:16, SEQ ID NO:18, SEQ ID NO:20, and SEQID NO:22.

In one embodiment the polypeptides are encoded by a polynucleotideselected from the group consisting of SEQ ID NO:1, SEQ ID NO:3, SEQ IDNO:5, SEQ ID NO:7, SEQ ID NO:9, SEQ ID NO:11, SEQ ID NO:13, SEQ IDNO:15, SEQ ID NO:17, SEQ ID NO:19, and SEQ ID NO:21. In anotherembodiment the polypeptides are encoded by other polynucleotides whichhave substantial identity to the herein described polynucleotides orthose which hybridize under stringent conditions.

Another object of the invention is to provide polynucleotide sequencesselected from the group consisting of SEQ ID NO:1, SEQ ID NO:3, SEQ IDNO:5, SEQ ID NO:7, SEQ ID NO:9, SEQ ID NO:11, SEQ ID NO:13, SEQ IDNO:15, SEQ ID NO:17, SEQ ID NO:19, and SEQ ID NO:21; as well as thosepolynucleotides that have substantial identity to these nucleotidesequences, preferably at least 95% identity.

Another object of the invention is to provide isolated polypeptideshaving a sequence selected from the group consisting of SEQ ID NO:2, SEQID NO:4, SEQ ID NO:6, SEQ ID NO:8, SEQ ID NO:10, SEQ ID NO:12, SEQ IDNO:14, SEQ ID NO:16, SEQ ID NO:18, SEQ ID NO:20, and SEQ ID NO:22; aswell as those polypeptides that have substantial identity to these aminoacid sequences, preferably at least 95% identity.

A further object of the invention is a method for producing a protein orproteins by culturing host cells containing the herein describedpolynucleotides under conditions and for a time suitable for expressionof the protein and collecting the protein produced thereby.

Another object is the use of host cells having the polynucleotidesdescribed herein to produce amino acids, as well as the use of suchisolated polypeptides in the production of amino acids.

Other objects of the invention include methods of detecting nucleic acidsequences homologous to at least one of: SEQ ID NO:1, SEQ ID NO:3, SEQID NO:5, SEQ ID NO:7, SEQ ID NO:9, SEQ ID NO:11, SEQ ID NO:13, SEQ IDNO:15, SEQ ID NO:17, SEQ ID NO:19, and SEQ ID NO:21, particularlynucleic acid sequences encoding polypeptides that herein describedproteins or polypeptides and methods of making nucleic acids encodingsuch polypeptides.

The above objects highlight certain aspects of the invention. Additionalobjects, aspects and embodiments of the invention are found in thefollowing detailed description of the invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Unless otherwise defined, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art of molecular biology. Although methods and materials similar orequivalent to those described herein can be used in the practice ortesting of the present invention, suitable methods and materials aredescribed herein. All publications, patent applications, patents, andother references mentioned herein are incorporated by reference in theirentirety. In addition, the materials, methods, and examples areillustrative only and are not intended to be limiting.

Reference is made to standard textbooks of molecular biology thatcontain definitions and methods and means for carrying out basictechniques, encompassed by the present invention. See, for example,Sambrook et al., Molecular Cloning: A Laboratory Manual, Third Edition,Cold Spring Harbor Laboratory Press, New York (2001), Current Protocolsin Molecular Biology, Ausebel et al (eds.), John Wiley & Sons, New York(2001) and the various references cited therein.

Corynebacterium glutamicum ssp. lactofermentum is a coryneform bacteriumhaving L-glutamic acid producing ability. The coryneform bacteriainclude the group of microorganisms defined in Bergey's Manual ofDeterminative Bacteriology, 8th edition, p. 599 (1974), which areaerobic Gram-positive rods having no acid resistance and nospore-forming ability and which can be used for the large-scaleproduction of a variety of fine chemicals including amino acids, nucleicacids, and so on. Corynebacterium glutamicum ssp. lactofermentum hashitherto been classified into the genus Brevibacterium as Brevibacteriumlactofermentum, but united into the genus Corynebacterium at present(Liebl, W. et. al., Int. J. Syst. Bacteriol., 41:255, 1991).

The polynucleotides of this invention can be used for tools forbiotechnology and also can be used to improve microorganisms, which areused to produce useful substances, for example, by fermentativeprocesses. Modulation of the expression of the polynucleotides encodinguseful activities of the present invention can be used to modulate theproduction of one or more substances from an organism.

Restriction endonucleases are indispensable for recombinant DNAtechnology and the diversity of specificity for recognition sequences isimportant for their usefulness as a tool. Restriction-modificationsystems are classified into three main types, according to their subunitcomposition, cofactor requirements, and some other features. AllRestriction-modification systems comprise a pair of enzymaticactivities—a DNA-methyltransferase and a restriction endonuclease, bothrecognizing the same short (4-8 bp) nucleotide sequence. Restrictionendonucleases catalyze double-stranded cleavage of DNA, while thefunction of methylases is to protect genomic DNA from cleavage bycognate specific endonucleases (Bickele, T. and Kruger, D. H.,Microbiol. Rev. 57:434-450, 1993). The usefulness ofrestriction-modification system for genome rearrangement has beenreported (Handa, N., Nakayama, Y., Sadykov, M., and Kobayashi, I., Mol.Microbiol. 40:932-40, 2001; Kobayashi, I., Nucleic Acids Res.29:3742-3756, 2001). The restriction-modification system is classifiedinto three types, namely, type I, II, and III. The type I systemconsists of three subunits, HsdM (DNA methylase), HsdS (specificityprotein), and HsdR (endonuclease) and function as complex of threesubunits. The type III system contain two subunits, one of which, Modcan function alone as a modification methylase. The second subunit Reshas no enzymatic activity when it is not complexed with Mod.

Molecular chaperones are substances that associate and stabilizeproteins at intermediate stages of folding, assembly, movement acrossmembranes, and degradation. It is widely recognized that co-expressionmolecular chaperones can assist recombinant protein folding expressed inEscherichia coli and that in at least some cases this leads to increasedproduction of active proteins (Nishihara, K., Kanemori, M., Kitagawa,M., Yanagi, H., Yura, T. Appl. Environ. Microbiol. 64:1694-1699, 1998).The most abundant and physiologically important chaperones include DnaK,DnaJ, GrpE, GroEL, and GroES. The DnaK is a member of the highlyconserved and ubiquitous stress-70 protein family, also known as thehsp70 family for heat shock protein-70, which bind to and stabilizeunfolded conformations of short regions of peptide chains (Gross, C. A.,Escherichia coli and Salmonella typhimurium Cellular and MolecularBiology (Neidhardt, F. C., Ingraham, J. L., Low, K. B., Magasanik, B.,and Umbarger, H. E., eds.) pp. 1382-1399, American Society forMicrobiology, Washington, D.C.).

Glutamate dehydrogenase (GDH) catalyses the conversion from2-oxoglutarate and NAD(P)H to L-glutamate and NAD(P). L-Glutamate is animportant metabolite, one of the primary ammonia assimilation products,a donor of amino groups in amino acid and purine biosynthesis, and aprecursor of the L-glutamate family of amino acids. The Corynebacteriumglutamicum gdh gene encoding NADP-dependent GDH has been isolated andanalyzed (Bormann, E. R. et. al., Mol. Microbiol., 6:317-26, 1992). Thisenzyme is one of the important enzymes for glutamate family amino acidproduction.

Proline and betaine (glycine-betaine) are major osmoprotectants in manyorganisms. The accumulation of osmoprotectants is an important processfor the adaptation to damaging environmental conditions. The increase ofosmoprotectants is achieved either by altering metabolism or bytransport (Csonka, L. N., Microbiol. Rev. 53:121-147, 1989). Thesecondary transporter ProP mediates the uptake of compatible solutes andcontributes to the osmotolerance (Peter, H. et. al. J. Bacteriol.,180:6005-12, 1998; Culham, D. E. et. al., Microbiology, 147:1657-70,2001). In Corynebacterium glutamicum, four secondary carriers forcompatible solutes have been identified: the high-affinity glycinebetaine uptake system BetP (Peter, H. et. al. J. Biol. Chem.273:2567-2574, 1998), the specific proline uptake system PutP (Peter, H.et. al., Arch. Microbiol. 168:143-51, 1997), the ectoine/proline/glycineuptake system EctP, and the proline/ectoine uptake system ProP (Peter,H. et. al., J. Bacteriol., 180:6005-12, 1998).

“Substantial identity” as used herein refers to polynucleotides andpolypeptides which are at least 70%, preferably at least 80% and morepreferably at least 90% to 95% identical to the polynucleotides andpolypeptides, respectively, according to the present invention.

“Polynucleotide” as used herein relates to polyribonucleotides andpolydeoxyribonucleotides, it being possible for these to be non-modifiedRNA or DNA or modified RNA or DNA.

“Polypeptides” as used herein are understood to mean peptides orproteins which comprise two or more amino acids bonded via peptidebonds. In particular, the term refers to polypeptides which are at least70%, preferably at least 80% and more preferably at least 90% to 95%identical to the polypeptides according to the present invention.Included within the scope of the present invention are polypeptidefragments of the polypeptides having a sequence selected from the groupconsisting of SEQ ID NO:2, SEQ ID NO:4, SEQ ID NO:6, SEQ ID NO:8, SEQ IDNO:10, SEQ ID NO:12, SEQ ID NO:14, SEQ ID NO:16, SEQ ID NO:18, SEQ IDNO:20, SEQ ID NO:22 or those which are identical to those describedherein.

“Polynucleotides which encode the polypeptide” of the invention as usedherein is understood to mean the sequences exemplified in thisapplication as well as those sequences which have substantial identityto the nucleic acid sequences at least one of: SEQ ID NO:1, SEQ ID NO:3,SEQ ID NO:5, SEQ ID NO:7, SEQ ID NO:9, SEQ ID NO:11, SEQ ID NO:13, SEQID NO:15, SEQ ID NO:17, SEQ ID NO:19, SEQ ID NO:21, and which encode amolecule having one or more of the bioactivities of the associated geneproducts. Preferably, such polynucleotides are those which are at least70%, preferably at least 80% and more preferably at least 90% to 95%identical to the nucleic acid sequences at least one of: SEQ ID NO:1,SEQ ID NO:3, SEQ ID NO:5, SEQ ID NO:7, SEQ ID NO:9, SEQ ID NO:11, SEQ IDNO:13, SEQ ID NO:15, SEQ ID NO:17, SEQ ID NO:19, and SEQ ID NO:21.

Polynucleotides according to the invention may be employed as probes toisolate and/or identify RNA, cDNA and DNA molecules, e.g., full-lengthgenes or polynucleotides which code for the polypeptides describedherein. Likewise, the probes can be employed to isolate nucleic acids,polynucleotides or genes which have a high sequence similarity oridentity with the polynucleotides of the invention.

Polynucleotides of the invention may also be used to design primersuseful for the polymerase chain reaction to amplify, identify and/orisolate full-length DNA, RNA or other polynucleotides with high sequencehomology or identity to the polynucleotides of the invention, as wellas, polynucleotides that encode the polypeptides of the invention.Preferably, probes or primers are at least 15, 16, 17, 18, 19, 20, 21,22, 23, 24, 25, 26, 27, 28, 29, or 30 nucleotides in length.Oligonucleotides with a length of at least 35, 40, 45, 50, 100, 150,200, 250, or 300 nucleotides may also be used.

Methods of DNA sequencing are described inter alia by Sanger et al.(Proc. Natl. Acad. Sci. USA, 74:5463-5467, 1977).

A person skilled in the art will find instructions for amplification ofDNA sequences with the aid of the polymerase chain reaction (PCR) interalia in the handbook by Gait: Oligonucleotide Synthesis: A PracticalApproach (IRL Press, Oxford, UK, 1984) and in Newton and Graham: PCR2^(nd) Edition (Springer Verlag, New York, 1997).

Additionally, methods employing DNA chips, microarrays, or similarrecombinant DNA technology that enables high throughput screening of DNAand polynucleotides that encode the herein described proteins orpolynucleotides with high sequence homology or identity to thepolynucleotides described herein. Such methods are known in the art andare described, for example, in Current Protocols in Molecular Biology,Ausebel et al (eds), John Wiley and Sons, Inc. New York (2000).

The polynucleotides and polypeptides of the present invention areproteins useful as biotechnological tools and for production ofsubstances, specifically identified in Corynebacterium glutamicum ssp.lactofermentum. By way of example, the present inventors provide thefollowing cited references (each of which are incorporated herein byreference) demonstrating that assays to assess the enzymatic activity ofthe polypeptides of the present invention are known and, as such,determination of whether a sequence falls within the scope of thepresent claims may be readily ascertained. These polynucleotides andpolypeptides include:

Type I restriction modification system, M subunit comprises the aminoacid sequence of SEQ ID NO:2 and is encoded by the hsdM1 gene whichcomprises the polynucleotide SEQ ID NO:1 (Gubler, M. et. al., EMBO J.11:233-240, 1992);

Type I restriction modification system, S subunit comprises the aminoacid sequence of SEQ ID NO:4 and is encoded by the hsdS1 gene whichcomprises the polynucleotide SEQ ID NO:3 (Gubler, M. et. al., EMBO J.11:233-240, 1992);

Type I restriction modification system R subunit comprises the aminoacid sequence of SEQ ID NO:6 and is encoded by the hsdR1 gene whichcomprises the polynucleotide SEQ ID NO:5 (Gubler, M. et. al., EMBO J.11:233-240, 1992)

Type I restriction-modification system, M subunit comprises the aminoacid sequence of SEQ ID NO:8 and is encoded by the hsdM2 gene whichcomprises the polynucleotide SEQ ID NO:7 (Gubler, M. et. al., EMBO J.11:233-240, 1992);

Type I restriction-modification system, S subunit comprises the aminoacid sequence of SEQ ID NO:10 and is encoded by the hsdS2 gene whichcomprises the polynucleotide SEQ ID NO:9 (Gubler, M. et. al., EMBO J.11:233-240, 1992);

Type I restriction modification system R comprises the amino acidsequence of SEQ ID NO:12 and is encoded by the hsdR2 gene whichcomprises the polynucleotide SEQ ID NO:11 (Gubler, M. et. al., EMBO J.11:233-240, 1992);

Type III restriction-modification system methyltransferase comprises theamino acid sequence of SEQ ID NO:14 and is encoded by the mod gene whichcomprises the polynucleotide SEQ ID NO:13 (Backer, O. D. and Colson, C.,Gene, 97:103-107, 1991);

Type III restriction modification system R protein comprises the aminoacid sequence of SEQ ID NO:16 and is encoded by the res gene whichcomprises the polynucleotide SEQ ID NO:15 (Backer, O. D. and Colson, C.,Gene, 97:103-107, 1991);

Chaperone protein DnaK2 comprises the amino acid sequence of SEQ IDNO:18 and is encoded by a dnaK2 gene comprising SEQ ID NO:17 (Zylicz, M.and Georgopoulos, C., J. Biol. Chem. 259:8820-8825, 1984);

Glutamate dehydrogenase Gdh2 comprises the amino acid sequence of SEQ IDNO:20 and is encoded by a gdh2 gene comprising SEQ ID NO:19 (Bormann, E.R. et. al., Mol. Microbiol., 6:317-326, 1992; Consalvi, V. et. al. Eur.J. Biochem. 196:459-467); and

Proline betaine uptake system ProP2 comprises the amino acid sequence ofSEQ ID NO:22 and is encoded by a proP2 gene comprising SEQ ID NO:21(Peter, H. et. al., J. Bacteriol., 180:6005-12, 1998).

The terms “stringent conditions” or “stringent hybridization conditions”includes reference to conditions under which a polynucleotide willhybridize to its target sequence, to a detectably greater degree thanother sequences (e.g., at least 2-fold over background). Stringentconditions are sequence-dependent and will be different in differentcircumstances. By controlling the stringency of the hybridization and/orwashing conditions, target sequences can be identified which are 100%complementary to the probe (homologous probing). Alternatively,stringency conditions can be adjusted to allow some mismatching insequences so that lower degrees of similarity are detected (heterologousprobing).

Typically, stringent conditions will be those in which the saltconcentration is less than approximately 1.5 M Na ion, typically about0.01 to 1.0 M Na ion (or other salts) at pH 7.0 to 8.3 and thetemperature is at least about 30° C. for short probes (e.g., 10 to 50nucleotides) and at least about 60° C. for long probes (e.g., greaterthan 50 nucleotides). Stringent conditions also may be achieved with theaddition of destabilizing agents such as formamide. Exemplary lowstringency conditions include hybridization with a buffer solution of 30to 35% formamide, 1 M NaCl, 1% SDS (w/v; sodium dodecyl sulphate) at 37°C., and a wash in 1× to 2×SSC (20×SSC=3.0 M NaCl/0.3 M trisodiumcitrate) at 50 to 55° C. Exemplary moderate stringency conditionsinclude hybridization in 40 to 45% formamide, 1 M NaCl, 1% SDS at 37°C., and a wash in 0.5× to 1×SSC at 55 to 60° C. Exemplary highstringency conditions include hybridization in 50% formamide, 1 M NaCl,1% SDS at 37° C., and a wash in 0.1×SSC at 60 to 65° C.

Specificity is typically the function of post-hybridization washes, thecritical factors being the ionic strength and temperature of the finalwash solution. For DNA-DNA hybrids, the Tm can be approximated from theequation of Meinkoth and Wahl (Anal. Biochem., 138:267-284, 1984):Tm=81.5° C.+16.6 (log M)+0.41 (% GC)−0.61 (% form)−500/L; where M is themolarity of monovalent cations, % GC is the percentage of guanosine andcytosine nucleotides in the DNA, % form is the percentage of formamidein the hybridization solution, and L is the length of the hybrid in basepairs. The Tm is the temperature (under defined ionic strength and pH)at which 50% of a complementary target sequence hybridizes to aperfectly matched probe. Tm is reduced by about 1° C. for each 1% ofmismatching; thus, Tm, hybridization and/or wash conditions can beadjusted to hybridize to sequences of the desired identity. For example,if sequences with approximately 90% identity are sought, the Tm can bedecreased 10° C.

Generally, stringent conditions are selected to be about 5° C. lowerthan the thermal melting point (Tm) for the specific sequence and itscomplement at a defined ionic strength and pH. However, severelystringent conditions can utilize hybridization and/or wash at 1, 2, 3,or 4° C. lower than the thermal melting point (Tm); moderately stringentconditions can utilize a hybridization and/or wash at 6, 7, 8, 9, or 10°C. lower than the thermal melting point (Tm); low stringency conditionscan utilize a hybridization and/or wash at 11, 12, 13, 14, 15, or 20° C.lower than the thermal melting point (Tm). Using the equation,hybridization and wash compositions, and desired Tm, those of ordinaryskill will understand that variations in the stringency of hybridizationand/or wash solutions are inherently described. If the desired degree ofmismatching results in a Tm of less than 45° C. (aqueous solution) or32° C. (formamide solution), it is preferred to increase the SSCconcentration so that a higher temperature can be used. An extensiveguide to the hybridization of nucleic acids is found in Tijssen,Laboratory Techniques in Biochemistry and MolecularBiology—Hybridization with Nucleic Acid Probes, Part I, Chapter 2“Overview of principles of hybridization and the strategy of nucleicacid probe assays”, Elsevier, New York (1993); and Current Protocols inMolecular Biology, Chapter 2, Ausubel, et al., Eds., Greene Publishingand Wiley-Interscience, New York (1995).

Stringent hybridization conditions are understood to mean thoseconditions where hybridization, either in solution or on a solidsupport, occur between two polynucleotide molecules which are 70% to100% homologous in nucleotide sequence which include 75%, 80%, 85%, 90%,95%, 98%, and all values and subranges therebetween.

Homology, sequence similarity, or sequence identity of nucleotide oramino acid sequences may be determined conventionally by using knownsoftware or computer programs. To find the best segment of identity orsimilarity of sequences, BLAST (Altschul et. al., J. Mol. Biol.215:403-410, 1990 and Lipman et. al., J. Mol. Biol. 215:403-410, 1990),FASTA (Lipman et. al., Science, 227:1435-1441, 1985), or Smith andWaterman (Smith and Waterman, J. Mol. Biol., 147:195-197, 1981) homologysearch programs can be used. To perform global alignments, sequencealignment programs such as the CLUSTAL W (Thompson et. al., NucleicAcids Research 22:4673-4680, 1994) can be used.

The present invention also provides processes for preparingsubstance-producing organisms that comprise at least one polynucleotidewhose expression is enhanced or attenuated. Likewise, the invention alsoprovides processes for preparing substance-producing organisms thatcomprise at least one polypeptide whose activity is enhanced orattenuated. Preferably, an organism with enhanced or attenuatedexpression of one or more of the polypeptides and/or polynucleotidesdescribed herein will improve amino acid yield at least 1% compared to abacterial strain not having the enhanced or attenuated expression. Forthe production of substances the polynucleotides described herein may beused to target expression, either by disruption to turn off or increaseor enhance the expression or relative activity of the polypeptideenzymes encoded therein.

The term “enhancement” as used herein means increasing intracellularactivity of one or more polypeptides in the producing orgamism, which inturn are encoded by the corresponding polynucleotides described herein.To facilitate such an increase, the copy number of the genescorresponding to the polynucleotides described herein may be increased.Alternatively, a strong and/or inducible promoter may be used to directthe expression of the polynucleotide, the polynucleotide being expressedeither as a transient expression vehicle or homologously orheterologously incorporated into the genome. In another embodiment, thepromoter, regulatory region and/or the ribosome binding site upstream ofthe gene can be altered to achieve the over-expression. The expressionmay also be enhanced by increasing the relative half-life of themessenger RNA.

In another embodiment, the enzymatic activity of the polypeptide itselfmay be increased by employing one or more mutations in the polypeptideamino acid sequence, which increases the activity. For example, alteringthe relative Km of the polypeptide with its corresponding substrate willresult in enhanced activity. Likewise, the relative half-life of thepolypeptide may be increased.

In either scenario, that being enhanced gene expression or enhancedenzymatic activity, the enhancement may be achieved by altering thecomposition of the cell culture media and/or methods used for culturing.

“Enhanced expression” or “enhanced activity” as used herein means anincrease of at least 10%, 25%, 50%, 75%, 100%, 150%, 200%, 300%, 400%,or 500% compared to a wild-type protein, polynucleotide, gene; or theactivity and/or the concentration of the protein present before thepolynucleotides or polypeptides are enhanced.

The term “attenuation” as used herein means a reduction or eliminationof the intracellular activity of the polypeptides in a cell that areencoded by the corresponding polynucleotide. To facilitate such areduction or elimination, the copy number of the genes corresponding tothe polynucleotides described herein may be decreased or removed.Alternatively, a weak and/or inducible promoter may used to direct theexpression of the polynucleotide, the polynucleotide being expressedeither as a transient expression vehicle or homologously orheterologously incorporated into the bacterial genome. For example, theendogenous promoter or regulatory region of the gene corresponding tothe isolated polynucleotides described herein may be replaced with theaforementioned weak and/or inducible promoter. Alternatively, thepromoter or regulatory region may be removed. The expression may also beattenuated by decreasing the relative half-life of the messenger RNA.

In another embodiment, the enzymatic activity of the polypeptide itselfmay be decreased or deleted by employing one or more mutations in thepolypeptide amino acid sequence, which decreases the activity or removesany detectable activity. For example, altering the relative Kd of thepolypeptide with its corresponding substrate will result in attenuatedactivity. Likewise, a decrease in the relative half-life of thepolypeptide will result in attenuated activity.

By attenuation measures, the activity or concentration of thecorresponding protein is in general reduced to 0 to 75%, 0 to 50%, 0 to25%, 0 to 10% or 0 to 5% of the activity or concentration of thewild-type protein or of the activity or concentration of the protein inthe starting microorganism.

Suitable vectors for carrying C. glutamicum ssp. lactofermentumpolynucleotides include those vectors which can direct expression of thegene in cells as known in the art. One embodiment of the presentinvention is whereby the vectors contain an inducible or otherwiseregulated expression system whereby the C. glutamicum ssp.lactofermentum polynucleotides may be expressed under certain conditionsand not expressed under other conditions. Furthermore, in anotherembodiment of the invention, the C. glutamicum ssp. lactofermentumpolynucleotides can be constitutively expressed. Examples of suchvectors and suitable cells in which they can be introduced are describedin Sambrook et al., Molecular Cloning: A Laboratory Manual, 3rd Ed.,Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y. (2001) andCurrent Protocols in Molecular Biology, Ausebel et al, (Eds.), JohnWiley and Sons, Inc., New York, 2000.

Methods of introducing C. glutamicum ssp. lactofermentum polynucleotidesor vectors containing the C. glutamicum ssp. lactofermentumpolynucleotides include electroporation, conjugation, calcium-mediatedtransfection, infection with bacteriophage, and other methods known inthe art. These and other methods are described in Sambrook et al.,Molecular Cloning: A Laboratory Manual, 3rd Ed., Cold Spring HarborLaboratory Press, Cold Spring Harbor, N.Y. (2001) and Current Protocolsin Molecular Biology, Ausebel et al, (Eds.), John Wiley and Sons, Inc.,New York (2000).

The invention also provides antibodies that bind to the polypeptides ofthe present invention. Antibodies binding to the polypeptides can beeither monoclonal or polyclonal, preferably the antibodies aremonoclonal. Methods for obtaining antibodies that bind to thepolypeptides are known in the art and are described, for example, inHarlow and Lane, Antibodies: A Laboratory Manual, Cold Spring HarborLaboratory Press, Cold Spring Harbor, N.Y. (1988).

Having generally described this invention, a further understanding canbe obtained by reference to certain specific examples which are providedherein for purposes of illustration only, and are not intended to belimiting unless otherwise specified.

General DNA manipulation was performed according to previously describedmethods (Sambrook et. al. (1989) “Molecular Cloning: A LaboratoryManual/Second Edition”, Cold Spring Harbor Laboratory Press). Wholegenome sequencing was performed using random shotgun method as describedby Fleischman R. D. et. al. (Science, 269:496-512, 1995).

EXAMPLE 1 Construction of Genomic Libraries of C. glutamicum ssp.Lactofermentum

Genomic DNA of a wild-type strain C. glutamicum ssp. lactofermentum ATCC13869 was isolated as described in (Y. Usuda et. al., Microbiology,142:3347-3354, 1996). The genomic DNA was sheared and fragmentized bysonication. The resultant fragments in the 1- to 2-kilo base pairs (kbp)size range were purified by gel electrophoresis through 1% agarose gel,followed by recovery using the QIAquick Gel Extraction kit (Qiagen K.K., Tokyo, Japan). The recovered fragments were blunted, phosphorylated,and ligated to the high-copy number vector pUC118 treated with HincIIand bacterial alkaline phosphatase (Takara Shuzo, Kyoto, Japan), usingBlunting Kination Ligation Kit (Takara Shuzo). This was designatedpUC118 library.

To get larger fragments, the genomic DNA was digested with varyingamounts of Sau3AI. One fraction containing the greatest mass of 30-40kbp range was selected by analyzing an aliquot of each fraction on 0.8%agarose gel electrophoresis. Another aliquot of the fraction wasdephosphorylated with calf intestine alkaline phosphatase (New EnglandBiolabs, MA, USA) and ligated into the BamHI site of cosmid vectorSuperCos 1 (Stratagene, Calif., USA) and followed by packging in kphage. This library composed of 30-40 kbp range fragments was designatedthe cosmid library.

EXAMPLE 2 DNA Sequencing and Sequence Assembly

The pUC118 library were introduced into Escherichia coli strain DH5α andplated on Luria-Bertani medium containing 100 μg/ml ampicillin and 40μg/ml 5-bromo-4-chloro-3-indolyl-α-D-galactoside (X-Gal). The whitecolonies were picked up and cultured in Luria-Bertani (LB) mediumcontaining 100 μg/ml ampicillin. The individual colony was cultured inthe well of the 96 deep-well plates, and the plasmids were isolatedusing QIAprep Turbo Kit (Qiagen). The DNA fragments inserted into pUC118were sequenced using a M13 reverse primer. The shotgun sequencing wasperformed with the BigDye terminators and 3700 DNA analyzer (AppliedBiosystems Japan, Tokyo, Japan). Approximately 55,000 samples frompUC118 library corresponding to coverage of over 8-fold to the genomesize were analyzed and the sequences were assembled by Phred/Phrapsoftware (CodonCode, MA, USA). From the assemble results, the cloneswhich assumed to link the contigs were picked up and sequenced by M13forward primer, M3. The re-assembly by Phrad/Phrap with Repeat Maskerprogram that exclude the repeat sequences yielded 52 contigs over 5 kbin length.

As for cosmid library, the packaged particles were introduced into E.coli strain XL1-Blue MR and selected on LB plates containing 25 μg/mlkanamycin. Approximately 900 clones corresponding to coverage of over10-fold were sequenced using both T3 and T7 universal primers. Based onboth the end-sequence data from the cosmid library and 52 contigsequences from the plasmid library, direct linkage between contigs wereestimated by using CAT (Clustering and Alignment Tools) software(Hitachi Ltd., Tokyo, Japan) and linking cosmid clones were selectedfrom the library. To fill gap region between contigs, sequences ofinserted fragments of the selected clones were determined by usingprimer-walking method. The further remaining gap regions betweencontigs, C. glutamicum ssp. lactofermentum genomic DNA were amplified byPCR using primers designed by the end-sequences of contigs, and theamplified products were sequenced directly by primer walking. The repeatsequences confirmed by resequening of PCR fragments amplified fromappropriate cosmid clones. Several regions were determined by sequencingin only one direction because of postulated secondary structures or highGC contents.

By this research, the genome of C. glutamicum ssp. lactofermentum wasfound to be a single circular form with the size of 3,272,733 bases andGC content of 54.2%.

EXAMPLE 3 Sequence Analysis and Annotation

Genome sequence analysis was managed by using the Genome Gamblersoftware (Sakiyama, T. et. al., Biosci. Biotechnol. Biochem., 64:670-673, 2000). The prediction of the protein-coding regions wasperformed by Glimmer 2.0 program (Delcher A. L. et al., Nucleic AcidsRes., 27:4636-4641, 1999), using a default condition with the sequence,5′-AAAGAGG-3′, as the Shine-Dalgarno sequence (Amador, E. et. al.,Microbiology, 145:915-924, 1999). The 3,545 open reading frames (ORFs)were extracted as putative protein-coding genes. The genome sequence ofC. glutamicum wild-type strain in DDBJ/EMBL/GenBank (BA000036) was usedas a reference. To determine the strain-specific genes, followingsuccessive homology searches at nucleotide level were executed. (1) Thehomology search using the BLASTN program (Altschul et. al., J. Mol.Biol., 215:403-410, 1990) with nucleotide sequences of ORF of eachstrain as queries against all ORF sequences was performed. From thesearch results, the ORFs from genomes of two strains with less than 100alignment length and with the score less than 100 were selected ascandidates for the next steps. (2) The homology search using the BLASTNprogram with candidate ORF sequences as queries against a whole genomesequence of the other strain. From homology search results, the ORFswith less than 100 alignment length and with the score less than 100were extracted as candidates for the next steps. The ORFs with less than300 bp in length were excluded from the candidates for thestrain-specific ORFs. (3) To confirm that these candidates forstrain-specific ORF does not show homology at amino acid sequence level,amino acid sequences were subjected to homology search using FASTAprogram (Lipman et. al., Science, 227:1435-1441, 1985) against all ORFsof the other strain. The ORFs that did not show homology to any aminoacid sequences of the other strain were treated as the strain-specificORFs. To estimate the function of the strain-specific ORFs, homologysearch of amino acid sequences were executed using the BLASTP programagainst non-redundant amino acid sequence database from GenBank.

As a result of homology search (1), 636 ORF were obtained as candidatesfor C. glutamicum ssp. lactofermentum strain specific ORFs. By thesearch (2), 424 ORFs were extracted as candidates of C. glutamicum ssp.lactofermentum strain specific ORFs from 636 ORFs used as querysequences. At this step, the ORFs with less than 300 bp in length wereexcluded and 220 ORFs were selected as candidates for strain specificORF in C. glutamicum ssp. lactofermentum. The homology search (3)revealed 12 ORFs showed significant homology with ORFs in C. glutamicumat amino acid sequence level. Finally, 208 ORFs were selected as the C.glutamicum ssp. lactofermentum strain-specific gene. From the BLASTsearch results against non-redundant protein sequences, carefulassignment of gene function was performed to identify the genes encodingthe useful genes in the biotechnology field. The two sets of type Irestriction-modification system (hsdM1-hsdS1-hsdR1 andhsdM2-hsdS2-hsdR2) and one of type III restriction-modification system(mod-res). The second dnaK gene (dnaK2) encoding molecular chaperoneprotein, the second glutamate dehydrogenase gene (gdh2), and the secondproline betaine uptake system gene (proP2) were identified.

Obviously, numerous modifications and variations on the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedherein.

While the invention has been described in detail with reference toexemplary embodiments thereof, it will be apparent to one skilled in theart that various changes can be made, and equivalents employed, withoutdeparting from the scope of the invention. Each of the aforementioneddocuments is incorporated by reference herein in its entirety.

1. An isolated polynucleotide encoding a protein comprising the aminoacid sequence of SEQ ID NO:20.
 2. A vector comprising the isolatedpolynucleotide of claim
 1. 3. An isolated host cell comprising theisolated polynucleotide of claim
 1. 4. The host cell of claim 3, whichis a Corynebacterium.
 5. A method of producing an L-amino acidcomprising culturing the host cell of claim 3 for a time and underconditions suitable for producing the amino acid; and collecting theamino acid produced.
 6. The method of claim 5, wherein said host cell isa Corynebacterium.
 7. An isolated polynucleotide comprising thenucleotide sequence of SEQ ID NO:19.
 8. A vector comprising the isolatedpolynucleotide of claim
 7. 9. An isolated host cell comprising theisolated polynucleotide of claim
 7. 10. The host cell of claim 9, whichis a Corynebacterium.
 11. A method of producing an L-amino acidcomprising culturing the host cell of claim 9 for a time and underconditions suitable for producing the L-amino acid; and collecting theL-amino acid produced.
 12. The method of claim 11, wherein said hostcell is a Corynebacterium.
 13. An isolated polynucleotide, whichhybridizes under stringent conditions to the isolated polynucleotide ofclaim 7, wherein said stringent conditions are hybridization in 50%formamide, 1M NaCl, and 1% SDS at 37° C., and a wash in 0.1×SSC at 60°C. to 65° C., and wherein said polynucleotide encodes a protein havingglutamate dehydrogenase Gdh2 activity.
 14. A vector comprising theisolated polynucleotide of claim
 13. 15. An isolated host cellcomprising the isolated polynucleotide of claim
 13. 16. A method ofproducing an L-amino acid comprising culturing the host cell of claim 15for a time and under conditions suitable for producing the L-amino acid;and collecting the amino acid produced.
 17. The method of claim 16,wherein said host cell is a Corynebacterium.
 18. An isolatedpolynucleotide, which is at least 95% identical to the polynucleotide ofclaim 7, and wherein said polynucleotide encodes a protein havingglutamate dehydrogenase Gdh2 activity.
 19. A vector comprising theisolated polynucleotide of claim
 18. 20. An isolated host cellcomprising the isolated polynucleotide of claim
 18. 21. A method ofproducing an L-amino acid comprising culturing the host cell of claim 20for a time and under conditions suitable for producing the L-amino acid;and collecting the L-amino acid produced.
 22. The method of claim 21,wherein said host cell is a Corynebacterium.